Image source, Reuters

Murray clenches his fist as Wawrinka's return whacks the tape and bounces back on the Swiss's side. Phew.

The pair become embroiled in a baseline rally, trading big blows like a couple of bare-knuckled fighters, until Wawrinka goes for the knockout blow with a forehand winner into the corner past Murray's stretching backhand.

And he's done it again! Wawrinka hammering down another forehand winner which is too hot for Murray to handle.

He's broken Murray!

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

Wawrinka just played with a bit of patience there. Murray had a bad bounce and was a little unlucky.

Image source, Getty Images

Oh no. Murray melts down with three unforced errors on his serve as Stan forces deuce, then produces the first double fault of the match at the worst possible time. Advantage Stan...

Easier said than done, Nick. Especially when Stan is thumping these balls back...

Nick: Murray needs better depth on his returns to have a chance. Getting away with it at the moment because of Stan's errors.

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

Image source, Getty Images

Wawrinka has a backhand which makes me scratch my head as to why he has not done well at Wimbledon.

It is the perfect shot for grass.

Refocus, refocus, refocus. That's what Wawrinka does, battering down a first serve out wide which Murray sticks strings on but can't divert to safety.

Murray gets back to deuce after another Stan unforced error, Wawrinka edging ahead when he gives Muzza the eyes to wrongfoot him with a forehand winner.

The Swiss third seed sees out the hold, but was again asked some serious questions by Murray.

A first sign of frustration from Murray, throwing his arms up in the air, after he is unable to return a deep incision by Wawrinka.

That's 30-15 to the Swiss, who then smacks an effortless forehand winner down the line. He makes it look easy.

Ah, jinxed him. Stan miscues his forehand for what is probably the first time, clubbing a cross-court shot into the tramlines. He went for that.

And then he goes for the next one - and again he missed the target. Back to deuce...

Image source, EPA

A brief pause as a couple of latecomers find their seats on Chatrier. I'm sure their petit dejeuner was worth it.

Murray isn't affected by having to wait a moment, a forehand volley kicking things off nicely, before a forehand winner puts him 40-0 ahead.

A meaty first serve is guided back over the baseline by Wawrinka, leading to a "Come on!" and a hold for Murray.

Piers Newbery
BBC Sport at Roland Garros

The divided ticketing system, which sees the two semi-finals treated as separate sessions with separate tickets for the first time, has not done wonders for the early crowd numbers. Chatrier is barely half full around the pricier lower stand, with more of those in the cheaper seats managing to get here for the crack of dawn (12.45pm local time).

Jiten Chandarana: When was the last time Murray won a match when he was not the favourite? (At least as far as the bookies are concerned)

Jamie Taylor: It's the French Open semi - where are all the fans??

Image source, Reuters

After coming under a bit of pressure on his previous service game, Wawrinka steadies the ship with an easy hold.

Two trademark backhand winners - perfectly timed and elegantly executed - seal the deal for the Swiss.

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

That last one was a better second serve from Murray. Wawrinka tried to return like he did earlier in the game.

Sometimes Stan can go on a roll like that but that second serve was too good that time.

A sumptuous cross-court backhand winner and a ferocious forehand later, we're back level pegging at 40-40.

Murray needs to dig deep, and he duly does. Stan gets his strings on two Murray returns but can't direct them to safety.

Muzza holds, we're still on serve.

Image source, Reuters

The Murray backhand drop-shot has been top drawer over the past couple of weeks. And here's Exhibit A.

The Scot pulls it out again, leaving Stan flapping at warm Parisian air as the ball spins away from his racquet like a Shane Warne leg-breaker.

That's 30-0 and Muzza is in command. Stan ain't going quietly though...

John Poole: Wawrinka is a monster. If Andy plays any less than 100% he'll be hit off the court in an hour and half

Not this time, Andy. Wawrinka plugs in and ramps up the voltage, Murray unable to control a forehand return from the baseline.

Break point turns into advantage Wawrinka, the Swiss cracking another winner - already his sixth of the match - to cling on.

Encouraging signs for the world number one though...

Image source, Reuters

A sniff of a break for Murray at 15-30, but that is quickly whipped away from him as a wicked Wawrinka forehand leaves him flapping.

Hang on, this is not over yet. Another unforced error from Stan brings up a break point for Murray...

Pat Cash
Former Wimbledon champion on BBC Radio 5 live

There is a little bit of a breeze out there.

It is quite tricky on the court, enough to make things interesting.